The present invention relates to a pneumatic tire, more particularly to a tire shoulder having a specific configuration being capable of improving wandering performance.
In order to prevent wandering of a vehicle during running on rutted roads, countermeasures taken on the pneumatic tires especially for heavy duty vehicles are providing axial cuts or sipes in the tread shoulder to decrease the rigidity, and rounding the tire shoulder with a relatively large radius to decrease the camber thrust.
When the axial sipes are provided, however, the tread rubber is liable to be torn off at the tread edge, and uneven wear is liable to occur along the sipes. These drawbacks are especially remarkable in case of heavy duty radial tires. When the tire shoulder is rounded by a relatively large radius, the ground contacting area decreases, and running performance such as road grip, cornering performance and the like are liable to deteriorate.
It is therefore, an object of the present invention to provide a pneumatic tire, in which wandering performance can be improved, while avoiding the above-mentioned drawbacks, i.e. tread rubber tear-off, uneven wear, ground contacting area decrease and the like.
According to the present invention, a pneumatic tire comprises
a tread portion with a pair of tread edges,
a tire shoulder extending radially inwardly from one of the tread edges, provided with a curved surface comprising a convex curve, and
on a cylindrical surface centered on the tire axis and intersecting said curved surface, said convex curve swelling axially outwards and having a curvature, the curvature gradually diminishing towards the radially inside from the tread edge.
It is possible that the tread portion is provided along the tread edges with a circumferentially extending rib and/or a circumferential row of blocks.
In case of circumferential rib, the rib is provided with the curved surface comprising a plurality of the convex curves and a plurality of convex curves alternating therewith so that the curved surface is waved in the tire circumferential direction.
In case of blocks in a circumferential row, it is preferable that each block is provided with the curved surface comprising at last one convex curve.